The invention relates to a turbomachine with at least one circulation structure, a circulation structure for a turbomachine and a method for inserting a circulation structure into a housing of a turbomachine.
Circulation structures and/or recirculation structures for turbomachines, such as gas turbines and their compressors in particular are known as so-called “casing treatments” and “hub treatments.” The circulation structures have primarily the task of increasing the aerodynamically stable operating range of the compressor by optimizing the pump limit interval. An optimized pump limit interval permits higher compressor pressures and thus a higher compressor load. The disturbances that are responsible for local compressor stall and ultimately for the pumping of the compressor occur at the housing-side ends of the rotor blades of one or more compressor stages and/or on the hub-side ends of the guide blades that are on the inside radially because the aerodynamic load on the compressor is greatest in these ranges. Flow in the region of the blade ends is stabilized by the circulation structures.
A turbomachine having such a circulation structure is disclosed in DE 10 2008 010 283 A1. The circulation structure is situated in the compressor of the turbomachine of a gas turbine in particular and has an annular space, which is oriented coaxially with the axis of rotation of a rotor of the turbomachine and is opened toward the main flow path. As seen in the main direction of flow of the main flow path, several chambers through which the flow passes in the axial direction are positioned upstream from the annular space. A turbomachine having such an alternative circulation structure is disclosed in EP 1 478 828 B1. This circulation structure also has an annular space that is oriented coaxially with the axis of rotation of a rotor of the turbomachine and is open toward the main flow path, but the annular space has a plurality of baffle elements disposed therein.
The object of the invention is to create a turbomachine having at least one circulation structure, which will facilitate insertion of the circulation structure into a housing of the turbomachine. In addition, another object of the invention is to create a circulation structure that can be inserted easily into a housing of a turbomachine. Furthermore, the object of the invention is to create a method for facilitating insertion of a circulation structure into a housing of a turbomachine.
A turbomachine according to the invention has at least one circulation structure, which has an annular space with baffle elements that extends around a main flow path and is open thereto. According to the invention, a housing of the turbomachine is divided into a front housing region and a rear housing region to receive the circulation structure in an axial plane of separation. Furthermore, in an axial plane of separation, the circulation structure is divided into a front structure region and a rear structure region in an axial plane of separation.
The division of the turbomachine housing to accommodate the circulation structure into at least two housing regions in combination with the division of the circulation structure into at least two structural regions simplifies the production and insertion of the circulation structure. The front structure region and the rear structure region may be formed by individual insertion and/or insert elements, paneling segments and/or liners and the like that are separated in the circumferential direction and can be assembled to form a ring, or ring segments that are closed in the circumferential direction. Likewise, the axial division of the turbomachine housing and the circulation structure allow the front structure region of the circulation structure to be inserted directly into the front housing region of the turbomachine, for example, because alternative milling paths and tools may be used due to the lateral access which is present due to the axial division. To do so, the circulation structure may be enlarged or designed to be more compact, for example. The terms “front” and “rear” here refer to the direction of flow of the main current flowing through the main flow path.
Insertion of the circulation structure can also be simplified if the axial plane of separation of the housing in the installed state is the same as the axial plane of separation of the circulation structure. To prevent the circulation structure from becoming stuck or jammed during assembly, the rear structure region in the assembled state may be set back slightly with respect to the planes of separation, so that after assembly, there is a minimal annular gap between the structure regions.
In one exemplary embodiment, the baffle elements are formed in the front structure region, which is inserted into the front housing region. In this exemplary embodiment, the front structure region is comprised of a plurality of insertion and/or insert segments, which are separated from one another in the circumferential direction and are manufactured separately from the front housing region. Alternatively, the front structure region is a single ring element, which is closed in the circumferential direction and is manufactured separately from the front housing region. The manufacture of the baffle elements can be simplified due to the separate production of the front housing region and the front structure region.
In one alternative exemplary embodiment, the baffle elements are inserted directly into the front housing region. This avoids separate insertion and/or insert segments and/or a separate ring element to form the front structure region, so that fundamentally fewer parts need be assembled. Furthermore, due to the integral design of the front structure region in the front housing region, the weight of the turbomachine and/or its housing is reduced.
The rear structure region is preferably an integral front body section of a paneling element inserted into the rear housing region. The paneling element may consist of a plurality of individual paneling segments divided in the circumferential direction, together forming a closed ring or a single paneling ring. The body section may be a retaining section of the paneling element for fastening the paneling element in or on the rear housing region so that no additional sections need be attached to the paneling element and/or its segments. Production of the baffle elements can be simplified due to the separate production of the rear housing region and the rear structure region. The paneling element preferably has an abradable lining, which extends in the circumferential direction and forms a closed ring, thereby preventing a bypass flow at the tip of the blade from a row of rotor blades opposite the paneling element.
A circulation structure according to the invention for a turbomachine has a structure housing, which is divided into a front structure region and a rear structure region in an axial plane of separation. The at least two-part design of the circulation structure simplifies its fabrication and in particular its integration into a turbomachine housing.
The efficiency of the circulation structure can be improved if it has baffle elements in the front structure region. The baffle elements may be at different lateral spacings from one another and may have different geometries and/or different angular positions. The baffle elements may thus have variable circumferential positions and geometries and/or courses, so that the circulation structure can be adjusted to the respective application case in a targeted manner.
With a method according to the invention for inserting a circulation structure into a housing of a turbomachine, a housing for the turbomachine is made available, having been subdivided into a front housing region and a rear housing region in an axial plane of separation. A front structure region of the circulation structure is then inserted into the front housing region, and a rear structure region of the circulation structure is inserted into the rear housing region. Next the housing regions are joined in the plane of separation.
This method permits a simple insertion and in particular an optimal alignment of the circulation structure due to the axial separation of the turbomachine housing in the region of the circulation structure and the axial separation of the circulation structure. Insertion here means both insertion of structure regions of the circulation structure manufactured separately from the turbomachine housing and an integral design of the structure regions in the turbomachine housing, for example, by means of a milling operation.
Air ducts are formed between the baffle elements in the front structure region, preferably in a single machining operation. Due to this measure the duration of manufacturing of the circulation structure is shortened in comparison with that of known manufacturing times. A finger milling cutter is an example of such a tool. The tool guide is preferably selected so that the flow properties of the baffle elements remain entirely or almost unaffected.
The rear structure region may be machined out, for example. In doing so, the rear structure region is formed integrally and/or directly in the rear housing section, so that fewer parts need be assembled. Furthermore, when the front structure region is formed directly in the front housing region by means of milling operations, for example, then virtually only the housing regions are to be assembled.
To adjust different or reduced transitional radii of the baffle elements from the base of the air ducts, for example, these may be machined separately after milling the air ducts. This can be accomplished, for example, by means of an alternative finger milling cutter with a reduced milling radius in comparison with the finger milling cutter used to form the air ducts.
Preferred exemplary embodiments of the invention are explained in greater detail below on the basis of schematic diagrams.